1. Field of the Disclosure
This disclosure relates generally to apparatus and methods for controlling hydraulic apparatus, including vehicles, such as zero turn radius vehicles and movable members.
2. Description of the Related Art
Various types of hydraulic apparatus utilize a variety of mechanical linkage systems to control fluid supply to pumps for controlling motion of work members. Examples of such hydraulic apparatus include zero turn radius (ZTR) machines, such as lawn machines or vehicles and movable members that perform industrial operations or move other elements or devices. In the case of ZTR machines, the hydraulic driven wheels are controlled by a mechanical linkage system. Such linkage systems provide linear motion to a hydraulic bi-directional pump/motor that rotates a wheel at a given rotational speed (revolutions per minute). Such vehicles are typically fitted with custom swash plates to provide a certain “feel” to the operator (driver) of the vehicle. The swash plate restricts or provides variable flow of a hydraulic fluid to the hydraulics at different points in a linear mechanical linkage system. Typically, such vehicles require adjustment to the swash plate prior to shipping to minimize the effects of mechanical tolerances in the system and to provide a specific feel to the operator.
The mechanical linkage and lever used to rotate the swash plate on each hydraulic pump is mounted so as the operator can apply a large amount of stroke to an arm (lever) to operate the vehicle. This allows a smooth control by limiting movement with a ratio-reducing lever to the wheels, as the lever moves forward and backward. As a result, the lever requires a moderate amount of work from the operator when used for long hours of operation. Such machines typically require the operator to use separate levers for each wheel of the vehicle. Such machines also do not offer adequate speed and acceleration control options for different skill levels of the operators and thus adequate safety for relatively inexperienced operators. Such vehicles typically do not include adequate in-situ calibration methods and thus can remain out of calibration until a service is performed.
Thus, there is a need for an improved apparatus and methods that address at least some of the above-noted needs.